I mean, he's by far the most "electable" of the GOP candidates for president.

He's got solid ground campaigns all across the country.

Rove and the moneyed establishment seems to be behind him.

His rivals on the right have proven to be embarrassing disasters, either rising quickly to the top and burning out almost as quickly (Bachmann, Perry) or never standing a chance (Santorum).

A fairly sensible middle-ground candidate never caught on and dropped out early (Pawlenty).

By far the best of the bunch, a remarkably sensible and genuinely impressive old-school Republican, hasn't caught on at all, as the party is both too extreme and too stupid to nominate him (Huntsman).

There's almost an inevitability about him, a sense that he'll prevail if only because his rivals are all so weak.

Unlike most of his rivals, he hasn't embarrassed himself badly on the campaign trail or in debates.

And he's managed to stay at or near the top in the polls without moving too far to the right, meaning that there's still a chance he could win some moderates and independents should he win the nomination.

Things are great! Right? Wrong.

First, if he wins, it will be largely by default, that is, only because the rest of the party, the anti-Romney majority, imploded, failing to vomit up a legitimate contender. The opposition to Romney in the GOP is extremely strong, while excitement for him is extremely small. Republicans will mostly still prefer him to Obama, if it comes to that, but what will Republican turnout be? Will conservatives stay home instead of voting for Romney?

Second, if he moves to the right to try to secure more conservative support, which he may have to do at some point, he'll lose moderate and independent support. But if he moves to the left, or even just stays where he is, he'll fail to arouse the GOP base, which, again, may stay home in droves next November. It may not matter, of course. No matter what he does, it's unlikely he'll ever be popular on the right, and it's hard to see a Republican winning without the Tea Party and social conservatives voting in big numbers.

Third, he would appear to have a low ceiling of potential support, and what support he does have is hardly intense. And while he has on occasion been called the frontrunner, even if at different times he has been surpassed by Bachmann, Perry, Cain, and now Gingrich, his poll numbers have remains consistent -- and consistently weak given his high profile and standing. Consider his Gallup numbers for the six months from June to November: 27, 23, 17, 24, 20, 21. His current RCP average is just 21.2. That puts him in first, ahead of Gingrich by a point and Cain by two, but, again, that's remarkably weak for someone who has been widely considered a frontrunner throughout the campaign so far, someone who has essentially been campaigning for president aggressively since 2007 (given that he ran for the 2008 GOP nomination as well). And if you add up the RCP averages of Gingrich, Cain, Perry, Paul, Bachmann, and Santorum, the non-Romney options, you get 62. Some of that support would certainly go to Romney, if without all that much enthusiasm, but regardless that's a sign of massive anti-Romneyism among Republicans. The clear message: conservatives do not like Mitt Romney and are looking desperately for an alternative.

Fourth, the party "elite," led these days it would seem by Karl Rove, may actually not have as much clout as you might think. It may very well want Romney to have the nomination, but the rest of the party, which in the past has usually fallen into line when it mattered, may not play along in 2012.

Fifth, at some point his rivals are going to go after Romney with greater focus and intensity than have so far. Perry has proven incapable so far, as has Cain, but what about Gingrich? He can certainly hold his own against Romney on policy, the media generally respect him as a man of ideas (however silly this may be), and he's got the rhetorical ability to challenge Romney on any number of issues, including, most notably, health-care reform. Indeed, what's amazing is that Romney's poll numbers are so relatively low despite the fact that he's been able to avoid, mostly because of the various weaknesses of his major rivals, significant criticism of his record, and specificially of his moderate and at times liberal past. Many Republicans know him as a flip-flopper and opportunist, as someone who will say anything to get elected, who will suck up to conservatives to try to win them over, but just think what they'd make of him if they actually knew what he was really all about. It's hard to imagine anyone like Romney cracking 10 percent in today's GOP.

On this last point, and specifically on health-care reform, Romney remains particularly vulnerable. That goes without say, I suppose, and yet his opponents haven't really gone after him yet on Romneycare, his reforms in Massachusetts. Pawlenty started but quickly retreated, pulling his punches, seemingly unable to rise to the occasion, and no one else has really made a big issue of it, preferring to try to out-extreme each other. It makes you wonder what the hell's wrong with them, until you realize what awful candidates they are, particularly Perry and Cain, neither of whom can seem to put a coherent thought together.

But the time may be coming, assuming that one of his rivals actually decides to focus on trying to take down Romney instead of wallowing in navel-gazing extremism. As Greg Sargent reported yesterday at WaPo:

Jonathan Gruber, the M.I.T. professor whose ideas were central to Mitt
Romney's health reform law as governor of Massachusetts, has pilloried
Romney in the past for seeming to distance himself from his signature
accomplishment. But I'm not sure he's ever gone quite as far as he did in this interview with Capital New York, in which he said Romney is flat out "lying" when he tries to make a distinction between Romneycare and Obamacare.

This is a massive invitation to Gingrich or Perry or someone at long last to make Romney's record the issue of the campaign. And it's easy to do. Here's the man behind both Romneycare and Obamacare, the man with the undeniable credibility to connect Romney directly to Obama on perhaps the top issue that arouses intense opposition among conservatives, calling Romney a liar. Sargent again:

I'm with Steve Benen and Jonathan Bernstein: Why aren't Romney's GOP rivals attacking him more aggressively over this? A recent Bloomberg poll
found that more than half of likely Iowa caucus goers would "rule out"
supporting Romney because of Romneycare's individual mandate. Why aren't
Romney's rivals hitting him harder over Romneycare, day in and day out?

Why isn't this an absolutely dominant issue in the GOP primary?

Maybe it's because Romney's rivals know that attacking him on this issue and others will only weaken him for the general election, assuming he wins the nomination. But at least a couple of his rivals are actually trying to win the nomination. Someone like Perry wouldn't hold back just because he thinks he's going to lose and wants to make sure Romney gets through this unscathed.

Maybe it's because his rivals are just so terrible. Cain can't even formulate an opinion about Libya. What is he to say about something as complicated policy-wise as health care? Perry's a bit better, but not much. So maybe it falls to Gingrich, not the leading anti-Romney candidate, to do the dirty work.

Regardless, things are obviously not great for Romney. He may still win the nomination, but right now, if you strip away the facade, he's weak and vulnerable. Conservatives already loathe him and want desperately to throw their weight behind a viable alternative (which is why they're going through his rivals one by one, hoping one of them will stick). All it may take is for one of his rivals to knock him out. The question is, is any of them up to it?